A. Field of the Invention
The present invention relates to blood vessel graft systems for repairing aneurysms, and more particularly to a catheter-based graft system for repairing aortic aneurysms by deploying a graft within a blood vessel via percutaneous entry into a femoral artery of a patient.
B. Description of the Prior Art
An aortic aneurysm is a very common deteriorating disease typically manifested by weakening and expansion of the aorta vessel wall at a region between the aorto-renal junction and the aorto-iliac junction. Aneurysms affect the ability of the vessel lumen to conduct fluids, and may at times be life threatening, for instance when rupture of the vessel wall occurs. A standard treatment for repairing an aneurysm is to surgically remove part or all of the aneurysm and implant a replacement prosthetic section into the vessel, however such surgery is generally postponed until the aneurysm has grown to a diameter greater than five centimeters. With aneurysms over five centimeters in diameter, the risk of complications is greater than the risks inherent in surgical excision and grafting of the aneurysm. Consequently, aortic aneurysms measuring greater than five centimeters in diameter, and those showing a rapid increase in size, are generally surgically removed and grafted as a matter of course, before rupture occurs.
The standard procedure for repairing an aortic aneurysm requires one or two days of preparing the large and small intestines prior to hospitalization. The operation itself generally takes one to three hours to perform, and necessitates several units of blood for transfusion. The patient commonly remains hospitalized for several days following surgery, and requires as much as three months recuperation time before returning to work. Moreover, there remain significantly high rates of mortality and morbidity associated with the standard procedure. The mortality rate is as high as eight percent, while the morbidity rate includes incident complications such as blood loss, respiratory tract infections, wound infections, graft infections, renal failure, and ischemia of the bleeding intestine. The mortality and morbidity rates for this type of major surgery are also often influenced by the fact that the typical aortic aneurysm patient is elderly and therefore less able to withstand major surgery, including anesthesia.
Other treatments for repairing an aneurysm involve deploying a graft device at the aneurysm site via a catheter traveling through a femoral artery. Conventional tubular aortic replacement sections, however, are generally considerably larger in diameter than the femoral artery and therefore cannot be inserted through the femoral artery lumen to the site of the aneurysm. Expandable graft devices suitable for catheter delivery and deployment have been proposed, as in U.S. Pat. Nos. 4,140,126 and 4,562,596 by Choudhury and Kornberg, respectively, however the expanding structures of the devices are cumbersome and difficult to operate.
U.S. Pat. No. 5,104,399 to Lazarus discloses an artificial graft device having staples at proximal and distal ends thereof for fixing the graft within the vessel, and a catheter-based deployment system including a tubular capsule from which the graft is deployed. The graft is of a preselected cross section and length, and is capable of being substantially deformed so as to accommodate to the interior surface of the blood vessel.
The majority of other graft systems, as exemplified by U.S. Pat. No. 5,304,220 to Maginot and U.S. Pat. No. 5,151,105 to KwanGett, require additional suturing or other methods for securing a graft. Furthermore, once a graft has been placed inside the lumen, adjustment usually requires a major surgical procedure.
Furthermore, the prior art stainless steel or elgialloy stent grafts carry high leakage rates. Moreover, high incidence of fractures have been associated with stainless steel stent grafts.
An additional problem with grafts in the public domain is the graft in-folding which causes leakage, migration, and thrombosis. Too, those grafts in the public domain such as U.S. Pat. No. 5,507,771 can provide adequate seals only with straight surfaces due to the spring shape and sealing force.
In cases where the aneurysm involves the ipsilateral and contralateral iliac vessels extending from the aorta, it is known to provide a generally Y-shaped bifurcated graft having a primary limb joining with an ipsilateral limb and a contralateral limb. An example of such a graft, and means for surgically implanting same, are described in U.S. Pat. No. 5,387,235 to Chuter. The surgical procedure taught by Chuter involves either surgical isolation of the femoral vessels in the groin to provide direct access to the vessels, or percutaneous entry through both ipsilateral and contralateral femoral arteries.
The difficulties involved with traditional surgical procedures and additional complexities associated with securing grafts make the treatment of aneurysms a very expensive and lengthy procedure. Thus, there exists a need for a treatment for aneurysms which requires minimal preparation and outpatient care, and which provides a safe and percutaneous method for deploying a graft capable of remaining in place without additional suturing or stapling for security.
Therefore, it is an object of the present invention to provide a graft which is deployable percutaneously by low-profile deployment means, and which provides a leak-proof conduit through the diseased region without suturing or stapling.
It is another object of the present invention to provide a bifurcated graft deployable through a single entry site.
It is yet another object of the present invention to provide an adjustable-length extension graft for coupling with a limb of a previously deployed graft.
It is yet another object of the present invention to provide low-profile graft deployment means capable of securely deploying a graft via percutaneous entry.
It is yet another object of the present invention to provide deployment means having inflatable and deflatable balloons for modeling a graft spring portion into conforming fixed engagement with the interior surface of a vessel, for dilating a vessel to facilitate insertion, and for controlling blood flow through a vessel during deployment of a graft.
It is yet another object of the present invention to establish an improved method for securely deploying a graft with minimal incision.
It is yet another object of the present invention to establish a method for implanting a graft with low mortality and low morbidity risks to patients.
It is yet another object of the present invention to establish a method for implanting a graft which requires less hospital and outpatient care than required by normal surgical grafting procedures.
It is yet another object of the present invention to establish a single-entry method for deploying a bifurcated graft.
It is yet another object of the present invention to is provide means for easily adjusting or removing an improperly deployed graft.
The present invention relates to an aneurysm repair system characterized by a graft apparatus which can be placed percutaneously via deployment means at the location of an aneurysm. It will be understood the term xe2x80x9cproximalxe2x80x9d as used herein means relatively closer to the heart, while the term xe2x80x9cdistalxe2x80x9d, as used herein means relatively farther from the heart.
The graft apparatus of the present invention comprises a tubular graft formed of bio-compatible graft material for conducting fluid, and may be in the form of either a straight single-limb graft or a generally Y-shaped bifurcated graft having a primary limb joining with a pair of lateral limbs, namely an ipsilateral limb and a contralateral limb, at a graft junction. A single-limb extension graft having a mating portion for coupling with a lateral limb of a bifurcated graft and an adjustable length portion extending coaxially from a distal end of the mating portion is also within the scope of the present invention. The graft material, preferably thin wall woven polyester or polytetrafluoroethylene (PTFE), is chosen so that the graft is capable of substantially deforming to conform to an interior surface of the blood vessel, and is preferably tapered through a middle portion of each limb. Other covering materials may be used, however, including micro-porous polyurethane, lycra, or cryogenically preserved explanted veins. The most preferred embodiment for the covering material is Lycra outside with thin PTFE inside at top proximal section with bare nitinol sinusoidal extension for above renal artery fixation. Further, for the aortic section, having aortic wall movement of approximately 3 MMS per heart beat, polyester (Dacron) is the preferred covering material. Moreover, with respect to grafts used in the iliac artery sections, where there is very little wall movement, PTFE is the preferred graft covering material. In the adjustable length portion of the extension graft, the graft material is crimped to permit axial or lengthwise extension and compression thereof.
The graft apparatus includes radially compressible spring means, preferably in the form of a nitinol wire spring having a pair of coaxially spaced annular spring portions connected by a connecting bar, for biasing proximal and distal ends of an associated graft limb or limb portion radially outward into conforming fixed engagement with the interior surface of the vessel. In the extension graft, an unpaired annular spring portion is located at a distal end of the adjustable length portion for similar biasing purposes. Each wire spring is enclosed by the graft material and stitched thereto, with cut-out portions being provided between spokes of the wire spring to define a plurality of radially distensible finger portions at the ends of the graft. A distal end of the contralateral limb of the bifurcated graft, and the distal end of the adjustable length portion of the extension graft, are each provided with a retainer ring to retain respective spring portions associated therewith in a radially compressed or loaded condition during deployment.
In a preferred embodiment, the graft apparatus further comprises a plurality of outer packets formed of a light degradable polymer and containing a tissue adhesive which is released by fiber-optic scope after the graft is implanted to bond the ends of the graft to the interior surface of the vessel and prevent leakage through micro-cracks therebetween. Medical grade expandable foam cuffs preferably surround the middle portion of the graft to promote clotting within the aneurysm sac. Alternatively, light actuated cryo precipitate fibrin glue may be painted onto the exterior surface of the graft material with a brush. The adhesive naturally remains as syrup until light actuates and cures. This replaces the need for packets and reduces the possibility of premature release of adhesive from packets that may break during deployment.
The deployment means of the present invention generally comprises an elongated sheath introducer having an axially extending sheath passage for slidably receiving the graft and maintaining the graft and associated spring means in a radially compressed pre-loaded condition prior to deployment of the graft within the vessel lumen, an elongated insertion catheter received within the sheath passage and pre-loaded graft for use in guiding the graft to the location of the aneurysm and deploying the graft within the vessel lumen at such location, and a flexible condensing spring push rod slidably arranged about the insertion catheter and received within the sheath passage to abut with the graft for navigating through tortuous vessels and pushing the graft out of the sheath passage during deployment. Deployment means may also comprise a micro-emboli filter tube selectively slidable over the sheath introducer and having controllable renal and iliac filters which may be opened to catch thrombus dislodged into the blood stream.
In one embodiment the push rod comprises a helical coil member. The push rod in this embodiment has a continuously variable stiffness so that the push rod may move flexibly throughout a tortuous vessel with minimal kinking of the sheath or other portions of the delivery system.
The insertion catheter of the present invention includes an embedded kink-resistant nitinol core wire and three inner tracks extending lengthwise thereof. A first inner track opens at both a near end and a remote end of the insertion catheter for receiving a guidewire to guide the insertion catheter through the vessel lumen. A second inner track opens at the near end of the insertion catheter for allowing fluid communication with an inflatable and deflatable tip balloon located at the remote end of the insertion catheter for dilating the vessel ahead of the graft and controlling blood flow through the vessel during placement. A third inner track opens at the near end of the insertion catheter for allowing fluid communication with an inflatable and deflatable graft balloon located near the remote end of the insertion catheter generally for securing the graft spring means against the interior surface of the vessel during graft deployment.
An optional spool apparatus may also be incorporated into the deployment means for collapsing a deployed graft and reloading the graft into sheath introducer 106 if unexpected leakage is observed due to incorrect graft position or size. The spool apparatus is connected to the sheath introducer and includes a plurality of suture loops wound around a spool cylinder and arranged to extend through a central axial passage of the push rod and around respective crests of a distal spring portion of the graft. A hand crank enables rotation of the spool cylinder to collapse the distal spring and pull it to within the sheath introducer, and a blade is provided on the spool apparatus for cutting each suture loop at one point to permit removal of the suture material if repositioning or removal of the graft is unnecessary.
A method of surgically implanting a pre-sized single limb graft to repair a previously-mapped aortic aneurysm using the deployment means of the present invention may be summarized as follows, keeping in mind that fluoroscopic or other monitoring means known in the art may be employed throughout the procedure.
First, a guide wire is introduced into the vessel via a femoral percutaneous entry and progressively inserted until a remote end of the guide wire extends upward past the aorto-renal junction, and the insertion catheter with surrounding pre-loaded graft, push rod, and sheath introducer are caused to follow the guidewire through the vessel lumen using the first inner track of the insertion catheter until the tip balloon is above the aorto-renal junction. The tip balloon may be partially inflated during insertion of the deployment means to dilate the vessel for easier introduction, and once properly positioned, may be inflated further so as to obstruct blood flow in the aorta just above the aorto-renal junction. With aortic blood flow obstructed, the insertion catheter is rotated so that the sheath introducer and compressed graft therewithin are best aligned to match the bends in the patient""s aorta. Next, the spring portion associated with the proximal end of the graft is observed for correct axial alignment within the vessel at a location just below the aorto-renal junction.
Once proper positioning and alignment of the apparatus are observed, the sheath introducer is withdrawn a short distance while holding the push rod in place to release the proximal spring portion of the graft from within a remote end of the sheath passage and allow it to expand radially outward to conform with the interior surface of the vessel, with verification being made that the proximal spring portion continues to be in correct position. The operator may remove the guidewire from the first inner track and inject contrast media into the first inner track, or may place an ultrasound imaging catheter, for purposes of visualization. Next, the insertion catheter is moved upward within the vessel to align the graft balloon to within the proximal spring portion of the graft, and the graft balloon is inflated with relatively high pressure to fixedly model the proximal spring portion against the interior surface of the vessel. The sheath introducer may now be withdrawn further to fully deploy the graft, including the distal spring portion, which should be located at a healthy region below the aneurysm.
Blood flow may then be gently introduced to the graft by slowly deflating the tip balloon. The graft balloon may be repeatedly deflated, moved incrementally along the central axis of the graft, and re-inflated to smooth out any wrinkles in the graft material. When the graft balloon has traveled down the graft to within the distal spring portion, it may again be inflated at a relatively high pressure to fix the distal spring in conformance with the inner surface of the vessel. If it is observed that the graft is not in its intended position, the spool apparatus of the present invention may be used to reload the graft within the sheath introducer.
Once the graft is correctly deployed, the deployment means may be completely withdrawn from the patient, and a fiber-optic scope inserted through the entry site to direct light at the tissue adhesive packets to cause the packet polymer material to degrade, thereby releasing the tissue adhesive. Finally, the entry site attended using standard procedure. Post-operative imaging may be conducted to verify isolation of the aneurysm, with particular attention being given to the occurrence of leaks at the proximal end of the graft closest to the heart.
The present invention also relates to a single-entry method of surgically implanting a pre-sized bifurcated graft in cases where mapping of the aneurysm indicates involvement of one or both iliac vessels.
Deployment of the bifurcated graft is carried out by a method similar to that used to implant a single-limb graft, except that additional procedures are required to properly implant a contralateral limb of the bifurcated graft within a contralateral iliac vessel. As the sheath introducer is withdrawn to deploy the primary leg of the graft within the aorta, the contralateral limb of the graft will be released from the sheath introducer when the sheath introducer has been withdrawn just past the graft junction, such that the contralateral limb of the graft is within the aneurysm sac or directed downward into the contralateral iliac vessel. The retainer ring at the distal end of the contralateral limb prevents premature expansion of the spring portion associated with such end to permit proper positioning of the contralateral limb within the contralateral iliac vessel.
Positioning of the contralateral limb is carried out using the insertion catheter and a deflectable guide wire inserted within the first inner track of the insertion catheter and having an inflatable and deflatable tip balloon at a remote end thereof. First, the graft balloon is deflated and the insertion catheter with inserted deflectable guide wire are withdrawn to the graft junction. A dial control may be used to deflect the remote end of the guide wire and direct it into the contralateral limb of the graft; the guide wire is then advanced deep into the contralateral iliac vessel and the tip balloon thereof is inflated to anchor the guide wire within the vessel. With its own tip balloon partially inflated, the insertion catheter is advanced along the anchored guide wire into the contralateral limb of the graft. The insertion catheter tip balloon is then inflated more fully to allow flow direction of blood to carry graft material of the contralateral limb down the contralateral iliac vessel. The contralateral limb is moved to a final desired location by deflating the insertion catheter tip balloon and advancing it to within the spring portion at the distal end of the contralateral limb held by the retainer ring, partially reinflating the tip balloon to hold the distal end and associated distal spring portion of the contralateral limb by friction, advancing the insertion catheter into the contralateral iliac vessel until the distal end of the contralateral limb is at the desired location, and finally reinflating the tip balloon fully to expand or break the retainer ring and release the spring portion. The deployment means may then be withdrawn and removed from the entry site and the entry site attended using standard procedure.
If the extent of disease indicates that a longer graft limb is necessary in either or both iliac vessels, an adjustable length extension graft may be coaxially coupled to a lateral limb, for instance the contralateral limb, of the bifurcated graft by the following procedure.
The extension graft is deployed via percutaneous entry through the contralateral femoral artery. A guide wire is directed through the contralateral limb and up into the primary limb of the bifurcated graft, and deployment means carrying a pre-loaded extension graft is directed over the guidewire to position the mating portion of the extension graft partially within the contralateral limb of the bifurcated graft such that a first spring portion at the proximal end of the mating portion is overlapped by the spring portion at the distal end of the contralateral limb. The sheath introducer may then be withdrawn while the push rod is held stationary to deploy the first spring portion, the insertion catheter moved upwards to locate the graft balloon within the first spring portion, and the graft balloon inflated to conform the first spring portion to the interior surface of the contralateral limb. Contrast media is injected through the first inner track of the insertion catheter to verify that the coupled graft limbs are not leaking. Next, the sheath introducer is further withdrawn to release a second spring portion defining a junction between the mating and adjustable-length portions, and a third spring portion at a distal end of the adjustable-length portion the radially retained distal annular spring of the adjustable length portion, into the contralateral iliac vessel. The graft balloon is then deflated and moved downward to within the third spring portion, and partially re-inflated to hold the distal end of the adjustable-length portion by friction. This permits the distal end of the adjustable-length portion to be positioned generally just above the sub-iliac or hypo-gastric branch by withdrawing the insertion catheter downward. The third spring portion is deployed by fully reinflating the graft balloon therewithin to expand or break the surrounding retainer ring and fix the third spring portion in conformance with the interior surface of the vessel. Any wrinkles in the extension graft may be removed using the graft balloon. Finally, once leakage has been ruled out, such as by angiogram verification, the deployment means may be withdrawn and the entry site attended.